Cam actuated collet



Jan- 15, 1957 H. D. PICKETT Erm. 2,777,703

CAM ACTUATED COLLET Filed Jan. 25, 1955 Il-I F1 g. l

w17 'TTORNEYSS/4 2,777,703 .CAM serveren flatter :HarQld.D..1BicBatt aadgLawreneetBenkwith, Sr., Riege,

.tricatisaeevafy .25 .1955 aerial N9- .48410.89 sciame (ci. ,21g-55) (Granted under Tifiess, u s. cette (1195;), seq. 256) The Mention .destbed .herein .may be manufaetuted nn'dfu' i d by'pr' for rthe' Gor/ ernment of thefUnitedStates 'of 'America for governmental purposes without.the =p ayV nient -tiffany royalties thereon ortherefor. ""{This'invention relatesto collets and more particularly tocollets which utilize a c am action to grip j the object to bens'upported, such as ashaft .or tool shank. f Mostlc'onventional vcollets for supportingdrills, sometimes referred to as drill chucks, relypn Y serrated jaws v'vhiclisecurely grip the drill shank. `lln some `of (these collets, key and ratchet construction on the chuck 'sleeve are provided yto assist the Aoperator in'manually eiierting the necessary clamping force.

An'inherentdisadvantage of theseconstructions is `that the drilhshanks are damaged :by the jaw indentation.

A`The indentations also encourage slippagebetween ythe jawsvand toolVand/results in severe scoring. Damage of type may reduce the life of the tools Vmore than the Yactual l drilling 'operation and represents a substantial tool' replacement'cost. Furthermore, thesecollets have a tendency to jam makingdrill release d ifncult.

' 'According to thepresent invention a collet is provided Twitha sleeve having a cavity that houses a plurality of circumferentially spacedjaws between which is vreceived ant object, such as a drill shank, to `be supported. Each .jaw is formed with an outer peripheral surfacecapable f rocking Ionthe inner cavity wall and an inner opposite lateral 4vs'l'nface vadapted to engage and wedge the object between .the other jaws when the jaws are rotated.v In

the preferred embodiment the cavity is cylindrical yand each outer jaw surface is curved having a smaller radins #than A'the radius of the cavity to permit the rocking action. Th'eiimer toolfengaging Asurfaces of the jaws c an bernade iiat toavoid scoring 'the peripheral surfaces of fthe ob ject since suiiicientclamping 4force is applied by thecam action. lTo permit adjustment of the'collet for `v arions sizes of drill Shanks, that portion of the cavity housing the jaws conical and the jaws correspondingly tapered and longitudinally positionable'to v ary thejaw opening. The sleeve is'provided with a suitable spindle connection Y..\gv l1 ic h can be a centr/alplunger having at the free end a 4,s :eigltering .recess to align the drill shank .within the Atleeteflle plunger .also serving t ferm au abutment for the inner ends of the jaws.

While prior Iart collets have been provided with a cam action, they could not be easily tightened and released nor did they oier a savings in increased tool life, simplicity in construction and operation, as well as other advantages of the present invention.

A primary object of this invention is to provide a collet capable of being tightened and released with a minimum of effort.

Another object is to provide a collet which will not score or otherwise damage the object supported whether it be a tool, shaft or the like.

Further objects are to provide a collet which is selftightening; to provide a drill chuck having a drill alignv2 ing rueanstandfto provide..l a. collet whichfs-simple ineenstruction and inexpensive to manufacture.

Other Objects and many of the attendantadvantases 0f fthiS-Vinventontwillbte-readily .appreciated asihersamethe- -eemes better 111.1derStQQd :byftefereuce .-to the. allewiug detailed description when` considered .fineeaneetientwith :the accompanying drawings .whereitt:

Fia ,1 tis .aside elevation Qf e Collet employed fa drill chuck;

:Fig- :.2 is enlarged y.etassfseetion ef .the .collet 0f its# 1 italien alensliae lle-IP .and

Fig. 3.jis ,a longitudinal ec on o f the,.col1etof Eig.;2 taken elqglinelIIf-flllnw I the drilL-.removfedtto Show .the details of Vthejaw.

s e ,effing new It0 .he drawing A.wherein .like .reference ehareeters.designate.lke-oreorresrcndins Pertsthreushjout the seVeralvieWS, thereis ,shown generallya collet lemployed asadrill chuckltl-comprising an outer knurled ys lemgfe 1 2 having acavity or bore V14 adapted'to housea pluralityzof circumferentially spaced :jaws `1 6 for clamp ing atoolshank 18 or the llikethat is inserted throughan open-sleeveend 2 0. In the preferred Iembodiment the borehas la circular cross-section, and is formed .with 4a c ylindrieal bore portion 22 and aconical bore portion 24,

.the qnialportion,enablingthe jaws to be longitudinally .adjusted to' accommodate a lvprescribed -range ,of ,dr-'ill ,Sizes- Jaws `16 are pcsitiouedinonicel bore ,portion 24 and are tapered toconform generally to the conicallsurface elthguahsmaller ,in length Ato aemit vradial expansion- The jews areresilientlv maintained in Seated tel tion, such as byfcoil tension springs 26, theppposite endspf each spring being secured in Asockets 28 'formedjinadjacent jaw surfaces.

The jaw assembly consists of preferably :three jaws 1 6, and, since each jaw can be identical `a description of 'one will suice for all. VEach jaw 1 6 is .provided with `an outer lateral surface ladapted Vto rock on the tapered beresurfaee fer e purpose te b'e-deseribed, and, prefer bly being curved, having a radius less than the rad1 thelconical bore at' any particular point of Contact -to ensure a rocking or rolling'rnovement. inneropposite lateral surface 32 of each jaw is adapted vto engage the round tool shank, and is'preferably dat vto avoid scoring the surface of theshank. Tool engagingsnrfagelis preferably cut at a bias with Arespect to the opposite jaw sides 34 to edect a cam action to clamp the drill shank therebetween when the jaws are rocked in a tightening direction. It has been found that the angleof c u t 1or bias of cam surface 32 of about lOdegrees with respect to one side will function satisfactory, the high sideldof the cam surface being on the driving 4side o f the jawdurine tightening .It is GbViQUS that the 4Side 3.4 ,Qfeaeh jaw @The high Side 0f @am .Surface 3.2 will be,19userthuthe opposite side. l The length of cam Isurface 32 will also determine the Smallest .Size V0f drill that .een be .accommodated. It shouldv be noted that vthe jaws are Yformed cross-section as sectors with adjacent sidesiijspaced s uiciently apart at any longitudinal position in conical boite position 2lito allow the rocking action.

Jaws 16 are backed-up in the chuck by an inner end 49 of a plunger 42 threadedly connected at 44 within the cylindrical portion 22 of the sleeve, the plunger being tapped at 46 on the outer knurled knob end 47 for connection to a drill spindle, not shown. A bushing 48 also threaded within bore portion 22 is provided with a smooth central opening 50 for guiding and aligning plunger end 40 to maintain the sleeve and jaws true with the spindle. A pair of slots 51 formed on the outer end of bushing 48 to enable the latter to be inserted within bore portion 22 and adjusted to the desired longitudinal position. The inner end face of plunger 42 is formed with a central depression 52 which functions as a self-centering seat for the drill shank. The removal of the chuck from the drill spindle is facilitated by provision of a hole 53 drilled into 'knob 47 to receive a rod or therlike whereby additional torque may be applied. Y Y

The operation of the drill chuck Ycan best be described with reference to Fig. 2, which shows drill shank 18 inserted between jaws 16 and initially clamped by camsurfaces 32 through the action of springs 26. The threading of plunger 42 into the sleeve applies a radial thrust by wedging the tapered jaws between the conical bore portion 24 and the drill shank, Y When a load is applied to the drill by engagement with a work piece, jaws 16 are rocked clockwise on the conical bore surface from the solid-line position to the brokenline position causing the drill shank to ride up the flat cam surfaces 32ftoward the high Ypoints 36, and the jaws in unison apply a radial thrust or pressure on the drill shank which increases in proportion to the load. As the cam surfaces are dat the Shanks are tightly clamped Without damage by scoring. To release the tool shank, jaws 16 can be easily rocked back to the initial solid-line posi tion where the drill shank rides down on cam surfaces 32 and the radial pressure on the drill shank is removed.

The collet of this invention enables a drill to be tightened and released easily and quickly Without the assistance of tools. The clamping surfaces of the jaws are smooth and cannot score the tool Shanks greatly lengthening toollife and reducing tool replacement. While the collet illustrated is used as a drill chuck, the novel construction can be utilized for -releasably gripping any object such as a shaft or the like.

Obviously many modications and variations of theY present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.y

We claim:

l. A collet comprising a sleeve having a cavity, a plurality of circumferentially spaced jaws -disposed within the cavity, means for maintaining said jaws in spaced relation, eachY of said jaws having an outer peripheral `surface adapted to rock on the wall of the cavity and only one inner opposite lateral cam surface adapted to engage the object to be secured, each lateral cam surface being continuous throughout its engaging surface and having a high point of engagement and a low point of engagement whereby rotation of the jaws on the sleeve wall will wedge the object between said high points of the cam surfaces.

2. A collet comprising a sleeve having a cavity, a plurality of circumferentially spaced jaws disposed within the cavity, means for maintaining said jaws in spaced relation, each of said jaws having an outer curved peripheral surface adapted to rock on the wall of the cavity and only one inner opposite lateral dat cam surface adapted to engage the object to be secured, each lateral cam surface being continuous throughout its engaging surface and having a high point of engagement and a low point of engagement whereby rotation of the jaws on the sleeve wall will wedge the objecttbetween said high points of the cam surfaces.

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3. `A collet comprising a sleeve having a conical cavity, a plurality of circumferentially spaced tapered jaws disposed within the cavity, means for maintaining said jaws in spaced relation, each of said jaws provided with an outer curved peripheral surface having a radius smaller than the radius of the cavity to permit each jaw to rock jaws on the sleeve wall will wedge the object between said high points of the cam surfaces.

, 4. A collet comprising a sleeve having a cylindrical cavi ity and a conical cavity in contiguous relation, a plurality of circumferentially spaced tapered jaws disposed Within the conical cavity, an axially movable plungermounted within the sleeve and having a centering aperture at the inner end to receive an object to be secured by said jaw, resilient means for maintaining said jaws in spaced relation, each of sai-d jaws provided with an outer curved peripheral surface havinga radius smaller than the radius of `the conicalavity to permit each jaw to rock on the Wall of the conical cavity,l each of said jaws also provided with only one inner opposite lateral iiat cam surface adapted to engage the object to be secured, each lateral cam surface being continuous throughout its engaging length and having a high point of engagement and a low point of engagement whereby rotation of the jaws .on the sleeve wall will wedge the object between said high points plunger adapted to abut the inner jaw ends, a bushing' threaded within said shell to receive and axially align said plunger, each of said jaws having sides and provided ywith an outer curved peripheral surface having a radiussmaller than the radius of the conical cavity to permit each jaw to rock on the conical cavity'wall, each of said jaws also provided with only one inner opposite lateral at cam sur- Y j face adapted to engage the object to be secured, one side of each jaw being longer than the other sideto provide a high point of engagement and a low point of engagement whereby rotation of the jaws on the sleeve wall will wedge the object between said yhighY points ofk the cam surfaces.

References Cited inthe le of this patent i Y UNITED STATES PATENTS 1,766,174 Hobbs et a1.;v June 24, 1930 2,535,106 vidal s- Dec. 26, 195o v 2,591,287 Penar et a1 Apr. 1, 1952 

